The present invention relates a remote control transmitter for remote-controlling various electronic appliances with infrared rays.
Recently, as various electronic appliances are developed and diversified in functions, remote control transmitters used for operations with them are provided with an illuminating function so as to be manipulated in a dark place.
A conventional remote control transmitter will be explained with referring to FIG. 4.
FIG. 4 is a circuit diagram of the conventional remote control transmitter. An operation key group 1 comprising translucent operation buttons and push switches. An internal memory (not shown) of a microcomputer 2 connected to the operation key group 1 stores several kinds of remote control transmission data for remote-controlling various electronic appliances such as a television and a video deck. Infrared ray output means 3 connected to the microcomputer 2 is serially connected to a driving transistor 4, a current limiting resistance 5, and an infrared ray light emitting diode (LED) 6. And further, a battery 7 is connected. A driving circuit 9 applies a specified voltage to an illuminating device 8 such as a light emitting diode or an EL disposed at the back of the operation key group 1, and makes the device illuminates it. A light switch 10 is disposed between the driving circuit 9 and battery 7 for turning on and off the driving circuit 9. They are covered with a case (not shown).
When any key in the operation key group 1 is manipulated, the remote control transmission data corresponding to the manipulated key stored in the internal memory is issued from the microcomputer 2 as an electric signal having a pulse waveform. The electric signal is amplified by the driving transistor 4 in the infrared ray output means 3. The current corresponding to the electric signal flows through the resistance 5, and thus, the LED 6 flickers and transmits the infrared ray signal to operate the electronic appliance.
When the light switch 10 is manipulated, the driving circuit 9 applies a specified voltage to the illuminating emitting device 8, and the device 8 illuminate the operation key group 1 from the back. That makes the operation key group 1 be manipulated easily in a dark place.
In the conventional remote control transmitter, when the operation key group 1 is manipulated while the illuminating device 8 is lit up, a current of about hundreds milliamperes flows in the LED 6, and thus, the voltage in the battery 7 is lowered. As a result, the applied voltage to the driving circuit 9 drops, and the luminance of the illuminating device 8 declines. Therefore, the illumination flickers, and the flickering makes to see the operation key group 1 hard.
An easy-to-operate and inexpensive remote control transmitter in provided in which the luminance of the illuminating device even when an operation key is manipulated without requiring drastic change from the prior art.
The remote control transmitter comprises the following parts:
(a) An operation key;
(b) A microcomputer including an internal memory for storing remote control transmission data, for issuing the data as an electric signal with the manipulation of the operation key;
(c) Infrared ray output means for issuing an infrared ray signal according to the electric signal issued by the microcomputer;
(d) An illuminating device for illuminating the operation key;
(e) A driving circuit for applying a specified voltage to the illuminating device for lighting up the illuminating device;
(f) A light switch for turning on and off the driving circuit; and
(g) A voltage control circuit including a diode having substantially the same power consumption as the infrared ray output means and being connected to the driving circuit, and a switching element connected parallel to the diode which is turned on and off by the electric signal issued by the microcomputer.